Jagemann Stephanie M, Juzwik Jennifer, Tobin Patrick C, Raffa Kenneth F
Department of Entomology, University of Wisconsin-Madison, Madison, WI.
USDA Forest Service, Northern Research Station, St Paul, MN.
Environ Entomol. 2018 Oct 3;47(5):1152-1164. doi: 10.1093/ee/nvy080.
Oak wilt is a lethal disease caused by the invasive fungus Bretziella fagacearum, which is transmitted belowground via root grafts and aboveground by sap beetles (Nitidulidae). Attempts to limit spread and impact of B. fagacearum emphasize limiting harvesting and pruning to periods of vector inactivity. However, there is limited information on sap beetle activity periods, responses to temperature, and phoresy frequencies of fungi. We sampled two major vectors in Wisconsin, Colopterus truncatus and Carpophilus sayi, for 2 yr to quantify their seasonal and geographic abundances. Trapping was performed in 12 oak stands, and beetles were assayed for B. fagacearum. C. truncatus was captured from March until November, peaking during April and May. C. sayi was captured from April until November, peaking in May and July. Relative abundances (N = 15,980) were 59.3% C. truncatus and 40.7% C. sayi. C. sayi was more abundant in southern Wisconsin, whereas C. truncatus was more evenly distributed. Both species were present at asymptomatic sites. All sites with oak wilt centers yielded beetles with viable fungal propagules, with the frequency of association ranging from 1 to 50%. Sites asymptomatic for oak wilt contained both beetle species, but no vector-borne viable pathogen. Degree-day models were constructed to improve the generality of these results and estimate cumulative emergences across a latitudinal range over the previous 10-yr means and extremes. Because activity by C. truncatus and C. sayi spans the seasonal activities of oak wilt vectors, these results can help guide oak management practices.
栎树枯萎病是一种由入侵真菌栎枯萎病菌（Bretziella fagacearum）引起的致命疾病，该真菌通过根部嫁接在地下传播，通过露尾甲（Nitidulidae）在地上传播。限制栎枯萎病菌传播和影响的措施主要强调将采伐和修剪限制在媒介不活动的时期。然而，关于露尾甲的活动时期、对温度的反应以及真菌的携带频率的信息有限。我们在威斯康星州对两种主要媒介——截尾筒喙象（Colopterus truncatus）和赛氏腐食酪螨（Carpophilus sayi）进行了为期两年的采样，以量化它们的季节和地理丰度。在12个栎树林分中进行诱捕，并对甲虫进行栎枯萎病菌检测。截尾筒喙象从3月到11月被捕获，4月和5月达到峰值。赛氏腐食酪螨从4月到11月被捕获，5月和7月达到峰值。相对丰度（N = 15980）为截尾筒喙象59.3%，赛氏腐食酪螨40.7%。赛氏腐食酪螨在威斯康星州南部更为丰富，而截尾筒喙象分布更为均匀。两种物种都出现在无症状的地点。所有有栎树枯萎病中心的地点都捕获到了带有活真菌繁殖体的甲虫，关联频率从1%到50%不等。没有栎树枯萎病症状的地点同时存在这两种甲虫，但没有媒介传播的活病原体。构建了度日模型以提高这些结果的普遍性，并根据过去10年的均值和极值估计跨纬度范围的累积出现量。由于截尾筒喙象和赛氏腐食酪螨的活动跨越了栎树枯萎病媒介的季节活动，这些结果有助于指导栎树管理实践。
